This invention relates generally to what are usually referred to in the art as trays and which are discussed specifically in U.S. Pat. No. 3,704,824. As stated in that patent, these trays are manufactured and sold in flat, knocked-down form and are therefore referred to as flats. That patent deals with forming strengthened corners in a flat between hinged side-wall flaps, the corners consisting of laminated connecting corner tabs which are arranged and maintained in superimposed relationship to produce a composite laminated flat corner structure, but which will not interfere with setting up the tray by merely folding outwardly the various flaps.
In the example disclosed in said patent, the flat was produced from a quadrangular sheet of suitable material scored and slit to provide a flat blank with the main flat wall and outwardly-extending hinged flaps at each edge thereof, the flaps being separated from each other at specifically formed corner slits running outwardly from the corner points of said wall. These slits and a pair of special adjacent corner fold score lines provided at each flap end, corner-connecting tabs of special form. The corner score lines at each corner were disposed at a right angle relatively and the slit at each corner extended outwardly from the junction of those score lines at an angle of 45.degree. to provide a pair of corner-connecting tabs of mainly triangular form. The end of the adjacent flap was provided with a scored fold line which extended from the corner point, at the junction of the corner score lines, at a 45.degree. angle relative to the adjacent corner fold score line and at a right angle relative to the corner slit into the flap and angularly to the outer edge thereof. Two of the opposed flaps of a first pair were folded inwardly and the two flaps of the second pair remained flat and extended outwardly so that the corner-connecting tabs were arranged in superimposed relationship and were maintained in that relationship by adhesive or otherwise to produce a composite laminated structure. The tray was set up for merely folding outwardly the first pair of flaps which automatically folded inwardly the second flat pair of flaps so that all the flaps were upstanding relative to the main flat wall. At the corner joints so produced by the connected tabs, there were two thicknesses of material with the tabs extending inwardly from the corner fold lines in opposite directions and overlapping the adjacent angularly disposed flaps which provide the side walls of flanges of the tray.